Modulation of erythropoiesis and myelopoiesis by exogenous erythropoietin in human long-term marrow cultures.
In spite of their ability to support myelopoiesis for several months, human long-term marrow cultures (LTMC) are unable to sustain the production of mature erythroid cells for greater than 4 weeks. Because this preference correlates with the presence of myeloid growth factors and possible absence of erythroid factors in LTMC, we studied the effects of the erythroid growth and differentiation factor erythropoietin (Epo) on both erythropoiesis and myelopoiesis in human LTMC. Either natural or recombinant Epo was added weekly to LTMC for 10 weeks, and total cell number, numbers of hemopoietic progenitors (mixed lineage colony-forming units, CFU-MIX; erythroid burst-forming units, BFU-E; erythroid CFU, CFU-E; granulocyte-macrophage CFU (CFU-GM); granulocyte CFU, CFU-G; and macrophage CFU, CFU-M), erythroblasts (early and late), granulocytes, and macrophages were quantitated separately in the adherent and nonadherent layers of the cultures. In the absence of Epo, mature erythroid cells disappeared within the first 3-4 weeks, whereas in cultures supplemented with Epo, erythropoiesis was supported for up to 8 weeks. Results indicate that erythroid maturation is blocked at the BFU-E stage and that exogenous Epo may act on a mature subpopulation of BFU-E located in the nonadherent fraction of the cultures, promoting its maturation into CFU-E, which in turn develop into erythroblasts. However, despite Epo supplementation, erythropoiesis was not restored to in vivo proportions, suggesting that additional factors or conditions necessary for erythropoiesis are lacking in LTMC. Interestingly, we found that exogenous Epo reduced the numbers of presumably more mature (nonadherent) myeloid CFU (CFU-C), granulocytes, and macrophages compared to controls and did not alter the levels of any of the most primitive hemopoietic progenitors measured (CFU-MIX, adherent BFU-E, and adherent CFU-C). Thus the data show that exogenous Epo modulates hemopoiesis in human LTMC, enhancing erythropoiesis and suppressing myelopoiesis, but that its effects appear limited to modulating levels of the nonadherent (more mature) progenitors, leaving the numbers of the adherent (immature) progenitor cells unchanged.
Mayani
H
H
Department of Medicine, University of Alberta, Edmonton, Canada.
Guilbert
L J
LJ
Janowska-Wieczorek
A
A
D001854:Bone Marrow Cells; D002478:Cells, Cultured; D003114:Colony-Forming Units Assay; D004900:Erythroblasts / Q000166:cytology; D004920:Erythropoiesis / Q000187:drug effects*; D004921:Erythropoietin / Q000494:pharmacology*; D006098:Granulocytes / Q000166:cytology; D006410:Hematopoiesis / Q000187:drug effects*; D006412:Hematopoietic Stem Cells / Q000166:cytology; D006801:Humans; D008264:Macrophages / Q000166:cytology
D004921:Erythropoietin